JPWO2015019909A1 - Centrifugal compressor and turbocharger - Google Patents

Abstract

An annular diffuser (27) is formed on the outlet side of the impeller (13) in the housing (5). A spiral scroll (31) is formed on the outlet side of the diffuser (27) in the housing (5). An annular recess (37) is formed inwardly in the radial direction at the boundary (35) between the shroud side wall surface (27s) of the diffuser (27) and the wall surface (31w) of the scroll (31).

Description

  The present invention relates to a centrifugal compressor that compresses a fluid (including gas such as air) using centrifugal force, and particularly relates to the periphery of a diffuser in the centrifugal compressor.

  In recent years, various research and development have been conducted on centrifugal compressors used in superchargers, gas turbines, industrial air facilities, and the like (see Patent Documents 1 to 3).

  A typical centrifugal compressor includes a housing. The housing has a shroud on the inside. An impeller is provided in the housing so as to be rotatable about its axis. The impeller has a disk. The hub surface of the disk extends from the one side in the axial direction of the turbine impeller toward the outside in the radial direction. A plurality of blades are integrally provided on the hub surface of the disk at intervals in the circumferential direction. The leading edge of each blade extends along the shroud of the housing.

  An annular diffuser (diffuser flow path) is formed on the outlet side of the impeller in the housing to decelerate and pressurize the compressed fluid (compressed fluid). Further, a scroll (scroll channel) communicating with the diffuser is formed on the outlet side of the diffuser in the housing.

JP 2009-2305 A JP 2006-220053 A JP 2010-196542 A

  By the way, during operation of the centrifugal compressor, flow separation (separation vortex) is generated at the outlet side of the shroud side wall surface of the diffuser due to a sudden change in the flow path shape. On the other hand, when flow separation develops, the effective flow path area on the exit side of the diffuser decreases. As a result, the mainstream flow cannot be sufficiently decelerated by the diffuser, and the static pressure recovery performance of the diffuser is reduced. In addition, a discharge port located on the downstream side of the scroll due to collision (interference) between the low-pressure part (blockage, low-pressure region, closed region) due to flow separation on the outlet side of the shroud side wall surface of the diffuser and the main flow in the scroll The flow in the (discharge flow path) is disturbed, and the compressor efficiency of the centrifugal compressor is reduced.

  Then, an object of this invention is to provide the centrifugal compressor and supercharger which can solve the above-mentioned problem.

  A first aspect of the present invention is a centrifugal compressor that compresses a fluid (including gas such as air) using centrifugal force, and includes a housing having a shroud on the inside thereof, and is rotatable in the housing. An impeller provided, a diffuser (diffuser flow path) formed radially outside the impeller outlet side in the housing, and a scroll formed on the outlet side of the diffuser in the housing and communicating with the diffuser (Scroll flow path), and the gist is that a recess is formed to be depressed inward in the radial direction at the boundary (boundary portion) between the shroud side wall surface of the diffuser and the wall surface of the scroll.

  In the specification and claims of the present application, “provided” means that it is indirectly provided via another member in addition to being directly provided, The phrase “provided integrally” includes including being integrally formed. The “axial direction” refers to the axial direction of the impeller, and the “radial direction” refers to the radial direction of the impeller. Furthermore, the “shroud side wall surface” refers to a wall surface located on a surface side obtained by extending the shroud of the housing outward in the radial direction.

  The gist of the second aspect of the present invention is that the turbocharger comprises the centrifugal compressor according to the first aspect.

  According to the present invention, during operation of the centrifugal compressor, the low pressure portion due to separation on the outlet side of the shroud side wall surface of the diffuser, in other words, the separation itself can be kept away from the mainstream flow in the diffuser. . Therefore, the main flow can be sufficiently decelerated by the diffuser while suppressing a decrease in the effective flow path area on the outlet side of the diffuser. Further, the separation of the low pressure portion due to the separation of the flow on the outlet side of the shroud side wall surface of the diffuser can be kept away from the mainstream flow in the scroll. Therefore, the collision (interference) between the low pressure portion and the main flow in the scroll can be reduced, and the disturbance of the main flow on the downstream side of the scroll can be suppressed. Therefore, according to the present invention, it is possible to improve the compressor efficiency of the centrifugal compressor while improving the static pressure recovery performance of the diffuser.

FIG. 1 is an enlarged view of an arrow I in FIG. FIG. 2A is an enlarged view of the arrow II in FIG. 1, and FIGS. 2B and 2C are views showing different embodiments of the recesses. FIG. 3 is a front sectional view showing a centrifugal compressor and the like according to the embodiment of the present invention. FIG. 4A is a schematic diagram showing a configuration around the diffuser according to the invention example, and FIG. 4B is a schematic diagram showing a configuration around the diffuser according to the comparative example. 5 (a) and 5 (b) are diagrams showing a region where a low pressure portion is generated in the operating region on the large flow rate side (choke side), and FIG. 5 (b) is a case where FIG. ) Is the case of the comparative example. 6 (a) and 6 (b) are diagrams showing static pressure distributions in the scroll and the diffuser in the operating region on the small flow rate side (surge side), and FIG. 6 (a) shows the case of FIG. (B) is a case of a comparative example. FIG. 7 is a diagram showing the relationship between the flow rate and the compressor efficiency in the case of the invention example and the comparative example.

  The present invention is based on the novel findings described below.

  That is, the new knowledge is that when an annular concave portion 37 is formed inwardly in the radial direction at the boundary (boundary portion) 35 between the shroud side wall surface 27s of the diffuser 27 and the wall surface 31w of the scroll 31 (FIG. 4 ( a))) as compared to the case where the annular recess 37 is not formed (see FIG. 4B), as shown in FIGS. 5A and 5B, during operation of the centrifugal compressor, On the outlet 27 o side of the diffuser 27 on the shroud side wall surface 27 s, a part of the low pressure part LP due to flow separation (separation vortex) enters the annular recess 37, so that the low pressure part LP enters the diffuser 27 and the scroll 31. It is possible to keep away from the mainstream flow (mainstream flow center line). Part of the low-pressure portion LP enters the annular recess 35 in addition to the mainstream flow itself in the scroll 31 and the pressure in the scroll 31 (the radially outer portion in the scroll 31) and the recess 35. This is probably due to the difference. In addition, the code | symbol 27i in Fig.4 (a) and FIG.4 (b) has shown the inlet_port | entrance of the diffuser 27 connected to the storage chamber (refer FIG. 1) of the impeller 13. FIG. Moreover, the recessed part 37 does not need to be a continuous cyclic | annular form, For example, you may provide a recessed part only in the area | region of the specific circumferential direction where the low voltage | pressure part LP appears notably. However, when the recess 37 is formed in an annular shape, machining becomes easy.

  Here, FIG. 4A is a schematic diagram showing a configuration around the diffuser 27 according to the invention example. FIG. 4B is a schematic diagram showing a configuration around the diffuser 27 according to the comparative example. 5 (a) and 5 (b) are diagrams showing a region where a low pressure portion is generated in the operating region on the large flow rate side (choke side), and FIG. 5 (b) is a case where FIG. ) Is the case of the comparative example. Further, the region where the low-pressure part LP is generated is obtained by numerical fluid analysis (CFD: Computational Fluid Dynamics analysis). Further, although not shown in the drawing, similar analysis results could be obtained not only in the operating region on the large flow rate side but also in the operating region near the peak of the compressor flow efficiency side (surge side).

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3. As shown in the drawing, “L” is the left direction and “R” is the right direction.

  As shown in FIG.1 and FIG.3, the centrifugal compressor 1 which concerns on embodiment of this invention is used for the supercharger 3, and compresses air using a centrifugal force.

  The centrifugal compressor 1 includes a housing (compressor housing) 5. The housing 5 includes a housing main body 7 having a shroud 7 s inside and a seal plate 9 provided on the right side of the housing main body 7. The seal plate 9 is integrally connected to another housing (bearing housing) 11 in the supercharger 3.

  An impeller (compressor impeller) 13 is provided in the housing 5 so as to be rotatable around its axis C. The impeller 13 is integrally connected to the left end portion of the rotation shaft 19. The rotating shaft 19 is rotatably provided in another housing 11 via a plurality of thrust bearings 15 and a plurality of (only one shown) radial bearings 17. Further, the impeller 13 includes a disk 21. The disk 21 has a hub surface 21h. The hub surface 21h extends outward in the radial direction (the radial direction of the impeller 13) from the left direction (one axial direction side of the impeller 13). Further, a plurality of blades 23 having the same axial length are integrally formed on the hub surface 21h of the disk 21 at intervals in the circumferential direction. The leading edge 23 t of each blade 23 extends along the shroud 7 s of the housing body 7. Instead of using the plurality of blades 23 having the same axial length, a plurality of types of blades (not shown) having different axial lengths may be used.

  An introduction port (introduction channel) 25 is formed on the inlet side of the impeller 13 in the housing body 7. The introduction port 25 introduces air into the housing 5. The inlet 25 is connected to an air cleaner (not shown) that purifies the air. A diffuser (diffuser flow path) 27 is formed on the outlet side of the impeller 13 in the housing 5. The diffuser 27 depressurizes and pressurizes compressed air (compressed air). The diffuser 27 is formed in an annular shape, for example. A throttle portion (throttle channel) 29 is formed between the impeller 13 and the diffuser 27 in the housing 5. The flow path width of the throttle portion 29 gradually decreases along the mainstream flow direction. The throttle portion 29 is formed in an annular shape, for example. The throttle unit 29 communicates with the diffuser 27.

  A scroll (scroll channel) 31 is formed on the outlet side of the diffuser 27 in the housing 5. The scroll 31 is formed in a spiral shape. The scroll 31 communicates with the diffuser 27. The cross-sectional area of the scroll 31 is larger on the winding end side (downstream side) than on the winding start side (upstream side). A discharge port (discharge flow path) 33 is formed at an appropriate position of the housing body 7. The discharge port 33 discharges compressed air to the outside of the housing 5. The discharge port 33 communicates with the scroll 31 and is connected to an engine side intake pipe (not shown) such as an engine intake manifold or an intercooler.

  As shown in FIGS. 1 and 2A, the shroud side wall surface 27s and the hub side wall surface 27h of the diffuser 27 are parallel to the radial direction (the radial direction of the impeller 13). Note that the shroud side wall surface 27s refers to a wall surface located on the surface side of the housing body 7 that extends the shroud 7s radially outward. The hub side wall surface 27h refers to a wall surface located on the surface side obtained by extending the hub surface 21h of the disk 21 outward in the radial direction.

  An annular recess 37 is formed at a boundary (boundary portion) 35 between the shroud side wall surface 27 s of the diffuser 27 and the wall surface 31 w of the scroll 31. The recess 37 is recessed inward in the radial direction. On the outlet 27o side of the diffuser 27 on the shroud side wall surface 27s, a low pressure portion LP is generated due to flow separation (separation vortex). The concave portion 37 allows a part of the low pressure portion LP to enter therein. Moreover, although the cross-sectional shape of the recessed part 37 shown to Fig.2 (a) is exhibiting V shape, the cross-sectional shape of the recessed part 37 is not limited to this. That is, the cross-sectional shape of the concave portion 37 is changed as appropriate, such as a U shape as shown in FIG. 2B or a rectangular shape as shown in FIG. Furthermore, if the annular recess 37 is formed to be recessed inward in the radial direction, the center line of the cross section of the recess 37 may be inclined with respect to the radial direction.

  The opening width (inlet width) α of the recess 37 is 20 to 80%, preferably 40 to 70% (0.20 to 0.80 times, preferably 0.40) of the flow path width β at the outlet of the diffuser 27. To 0.70 times). The reason why the opening width α is set to 20% or more of the flow path width β is less than 20%, the opening width α of the concave portion 37 becomes small, and a part of the low-pressure portion LP does not easily enter the concave portion 37. Because there is a fear. The opening width α is set to 80% or less of the flow path width β at the outlet of the diffuser 27. If the opening width α exceeds 80%, a part of the main flow in the scroll 31 flows into the recess 37 and the scroll This is because the pressure difference between the inside 31 and the recessed portion 37 becomes small, and as a result, a part of the low pressure portion LP may not easily enter the recessed portion 37.

  The recess amount δ of the recess 37 is set to 0.5 to 5.0 times, preferably 2.0 to 3.0 times the opening width α of the recess 37. The reason why the depression amount δ is set to 0.5 times or more of the opening width α is less than 0.5 times, so that even if a part of the low-pressure portion LP enters the recess 37, the low-pressure portion LP is placed in the diffuser 27. This is because it may be difficult to keep away from the mainstream flow (mainstream flow center line) in the scroll 31. In addition, the depression amount δ is set to 5.0 times or less of the opening width α. If the amount exceeds 5.0 times, a part of the main flow in the scroll 31 flows into the recess 37 and the bottom of the recess 37 This is because when the stagnation pressure on the side increases, a part of the low-pressure part LP may not easily enter the recess 37.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  The air introduced into the housing 5 from the inlet 25 can be compressed by rotating the impeller 13 integrally with the rotary shaft 19 around its axis by driving a radial turbine (not shown) in the supercharger 3. it can. The compressed air (compressed air) is pressurized while being decelerated by the diffuser 27 and is discharged from the discharge port 33 to the outside of the housing 5 via the scroll 31.

  An annular recess 37 is formed at the boundary 35 between the shroud side wall surface 27s of the diffuser 27 and the wall surface 31w of the scroll 31 so as to be recessed inward in the radial direction. Therefore, when the above-mentioned new knowledge is applied, during the operation of the centrifugal compressor 1 (during operation of the turbocharger 3), the flow is separated (exfoliation vortex) on the shroud side wall surface 27s on the outlet 27o side of the diffuser 27. A part of the low-pressure part LP enters the annular recess 37. As a result, the low-pressure part LP can be kept away from the main flow (main flow center line) in the diffuser 27 and the scroll 31. In other words, the low-pressure portion LP can be displaced to a location that does not hinder the main flow in the diffuser 27 and the scroll 31.

  Therefore, according to the embodiment of the present invention, during operation of the centrifugal compressor 1, the low pressure portion LP due to the separation of the flow on the outlet 27o side of the diffuser 27 on the shroud side wall surface 27s, in other words, the separation itself is the diffuser 27. Away from the mainstream flow. Therefore, the reduction of the effective flow path area on the outlet 27o side of the diffuser 27 can be suppressed and suppressed. Therefore, the mainstream flow can be sufficiently decelerated by the diffuser 27. Further, the separation of the low pressure portion LP due to the separation of the flow on the outlet 27 o side of the diffuser 27 on the shroud side wall surface 27 s can be kept away from the mainstream flow in the scroll 31. Therefore, the collision (interference) between the low-pressure part LP and the main flow in the scroll 31 can be mitigated, and the disturbance of the main flow in the discharge port 33 located on the downstream side of the scroll 31 can be suppressed. Therefore, according to the present invention, it is possible to improve the compressor efficiency of the centrifugal compressor 1 while enhancing the static pressure recovery performance of the diffuser 27.

  The present invention is not limited to the description of the above-described embodiment. For example, the technical idea applied to the centrifugal compressor 1 can be applied to a gas turbine, an industrial air facility, or the like, or the diffuser vane can have a plurality of diffuser vanes. In addition, the present invention can be implemented in various modes, such as arranging (not shown) at intervals in the circumferential direction. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

  An embodiment of the present invention will be described with reference to FIGS. 6 (a), 6 (b) and 7. FIG.

  For the invention example (see FIG. 4 (a)) and the comparative example (see FIG. 4 (b)), numerical fluid analysis was performed on the static pressure distribution in the scroll and diffuser in the operating region on the small flow rate side (surge side). It was. As a result, it was confirmed that the inventive example shown in FIG. 6A can increase the static pressure in the scroll as a whole as compared with the comparative example shown in FIG. In other words, it was confirmed that the static pressure recovery performance of the diffuser can be enhanced. Although not shown, similar analysis results could be obtained not only in the operating range on the small flow rate side but also in the operating range near the high flow rate side and the peak of the compressor efficiency. The numerical values in FIGS. 6A and 6B are obtained by making the static pressure in the scroll dimensionless.

Numerical fluid analysis was performed on the relationship between the flow rate and the compressor efficiency in the inventive example (see FIG. 4A) and the comparative example (see FIG. 4B). As a result, as shown in FIG. 7, it was confirmed that the inventive example improves the compressor efficiency in a wide operating region from the small flow rate side to the large flow rate side as compared with the comparative example.

A first aspect of the present invention is a centrifugal compressor that compresses a fluid (including gas such as air) using centrifugal force, and includes a housing having a shroud on the inside thereof, and is rotatable in the housing. An impeller provided, a diffuser (diffuser flow path) formed radially outside the impeller outlet side in the housing, and a scroll formed on the outlet side of the diffuser in the housing and communicating with the diffuser (Scroll channel), and a recess is formed in the boundary (boundary portion) between the shroud side wall surface of the diffuser and the wall surface of the scroll . and gist 0.5-5.0 Baidea Rukoto opening width of the recess.

Claims (6)

A centrifugal compressor that compresses fluid using centrifugal force,
A housing having a shroud inside;
An impeller provided rotatably in the housing;
A diffuser formed radially outward on the outlet side of the impeller in the housing;
A scroll formed on the outlet side of the diffuser in the housing and communicated with the diffuser;
Comprising
A centrifugal compressor, wherein a concave portion is formed to be depressed radially inward at a boundary between a shroud side wall surface of the diffuser and a wall surface of the scroll.   2. The centrifugal compressor according to claim 1, wherein an opening width of the concave portion is set to 20% or more of a flow path width of an outlet of the diffuser.   2. The centrifugal compressor according to claim 1, wherein a recess amount of the recess is set to be 0.5 times or more of an opening width of the recess.   The centrifugal compressor according to claim 2, wherein the amount of depression of the recess is set to be 0.5 times or more the opening width of the recess.   The centrifugal compressor according to any one of claims 1 to 4, wherein the recess is formed in an annular shape. A turbocharger comprising the centrifugal compressor according to any one of claims 1 to 5.

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